The effect of the temperature of Na-Y zeolite treatment with ethylenediaminetetraacetic acid on its structure

Abstract

The variations in the structure of Na-Y zeolite after its dealumination with ethylenediaminetetraacetic acid at 293 and 373 K were studied by IR spectra of lattice vibrations. The resulting deformation of the terminal [O3SiO](H,Na) tetrahedra is accompanied by the closure of the terminal ≡Si-O(H,Na) groups with the formation of bridge bonds. The saturation of samples dealuminated at 373 K with water decreases the deformation of the terminal tetrahedra which recovers on heating. Long-term exposure to water vapor results in an irreversible decrease in local deformations and in lowering the excessive negative charge of the skeleton, which manifests itself in a general high-frequency shift of the bands by 5–7 cm−1. These changes are more pronounced when the samples are heated in air at 873 K. The local structure deformations of the samples dealuminated at 293 K are irreversible. Heating them at 873 K causes the reorganization of the structure with the formation of a silica phase.